. >> reporter: mark and diane williams first met mary at saint ann an's hospital in july of 2010, a preemie weighing two pounds and 10 ounces. they took her into their oxen hill home as foster parents, loved and nourished her up to her current weight of 23 pounds and started working right away to make her theirs forever. >> i said i didn't care how long it took as long as we got her and it was a happy day today. >> reporter: happy, because today their adoption was finalized with 20 other families at d.c.'s annual adoption day ceremony. the event not only celebrating the joy of adoption, but it's meant to consider others to consider adopting or fostering a child. right now, there are 120 children in pc foster care waiting for adoptive families. mary is the ninth child the williams have fostered. >> mary's the one that we got to adopt out of nine children. we're happy for her and my family. >> reporter: it took two years for the day to come, but the weight is over. >> there is paperwork, reports, court hearings -- all kinds of things that go into finalizing the adoption and we were just so ha